An imaging apparatus having an auto-focus (AF) function has a distance metering device that measures a distance to a photographic subject. A plurality of distance measurement methods used for the distance metering device are known. For example, triangulation is known as a distance measurement method (see Japanese patent number 3761383). A distance metering device disclosed in Japanese patent number 3761383 (in Japanese patent number 3761383, it is described as an external AF sensor) has a pair of lenses for distance measurement that are arranged at a predetermined interval, and image sensors for distance measurement that are arranged corresponding to each of the lenses for distance measurement. Each of the image sensors for distance measurement has a light-receiving surface, and forms an image of a photographic subject on the light-receiving surface through each of the lenses for distance measurement. Based on the image of the photographic subject formed on each light-receiving surface, a pixel signal is outputted from each of the image sensors for distance measurement. Parallax is calculated by use of those two pixel signals, and based on the parallax, the distance to the photographic subject is calculated.
As for the distance metering device using triangulation as in the above, it is necessary for light-receiving surfaces of two image sensors for distance measurement to be precisely arranged on the same flat surface. That is, each light-receiving surface of each of the image sensors for distance measurement is not supposed to have an angle shift. And additionally, it is necessary for each light-receiving surface of each of the image sensors for distance measurement to be precisely arranged at a position that is a predetermined distance (length of baseline) away from each other. Therefore, in a conventional distance metering device to which triangulation is applied, precise arrangement of the image sensors for distance arrangement on a circuit board in a production process is required, and an adjustment operation for a position shift and an angle shift becomes troublesome. Accordingly, productivity of such a distance metering device is poor.
Therefore, it is known that in a distance metering device in which an adjustment operation in the production process does not become troublesome, each light-receiving surface of the image sensors for distance measurement is arranged on the same flat surface, and positioned at a predetermined distance away from each other, and further a parallax calculation circuit that is arranged on the same semiconductor on which the image sensors for distance measurement are arranged is included (see Japanese patent application publication number 2007-322128).